Method and entity for transmitting in a communications system

ABSTRACT

The disclosure relates to a method performed in an entity for transmitting in a communications system. The method comprises assessing a channel to be available for transmission by establishing an on-going transmission to have a received signal strength such as to allow simultaneous transmission in view of a first clear channel assessment threshold; establishing type of transmission of the on-going transmission; and determining, based on the established type of transmission, whether to transmit or to defer transmitting. A corresponding entity, computer programs and computer program products are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/746,722, which has a section 371(c)(1) date of Jan. 22, 2018(published as US 20180220460 on Aug. 2, 2018), and which is the nationalstage of International patent application No. PCT/SE2015/050831, filedJul. 22, 2015. The above identified applications and publication areincorporated by this reference.

TECHNICAL FIELD

The technology disclosed herein relates generally to the field ofwireless communications networks, and in particular to methods forhandling transmissions in such networks.

BACKGROUND

Wi-Fi, also known as Wireless Local Area Network (WLAN), is a technologythat currently mainly operates on the 2.4 GHz or the 5 GHz band. Thereare specifications regulating an access points' or wireless terminals'physical (PHY) layer, medium access layer (MAC) layer and other aspectsin order to secure compatibility and inter-operability between differentWLAN entities, e.g. between an access point and mobile terminals, bothof which may be referred to as stations (STAs) in the following. Wi-Fiis generally operated in unlicensed bands, and as such, communicationover Wi-Fi may be subject to interference sources from any number ofknown and unknown devices. Wi-Fi is commonly used as wireless extensionsto fixed broadband access, e.g., in domestic environments and hotspots,like airports, train stations and restaurants.

The WLAN technology relies on a procedure known as Carrier SensingMultiple Access with Collision Avoidance (CSMA/CA) in order toefficiently and in a fair way share the wireless medium among thedifferent WLAN entities (STAs) and among different Radio AccessTechnologies (RATs). The CSMA/CA procedure applied in the WLAN systemdemands that each entity that wishes to send data senses the commoncommunication channel before performing a transmission. Such sensing, orscanning, is done in order to avoid that simultaneous transmissions aremade, which usually results in loss of data and need forretransmissions.

FIG. 1 illustrates, in a simplified manner, a clear channel assessment(CCA), applied by a STA that has a frame to transmit (box 1). In orderto assess if a channel is busy, the STA starts scanning (box 2) thechannel. If the STA detects a transmission, it establishes the receivedsignal strength thereof. If the received signal strength is higher thana pre-determined threshold, referred to as Clear Channel Assessmentthreshold (CCAT), then the STA deems the channel as busy and defers itsown transmission (box 3). If the STA does not detect any such receivedsignal strength, it assumes the channel to be idle and transmits theframe (box 4).

FIG. 2 illustrates an example of a Basic Serving Set (BSS) comprising anaccess point AP and a number of user entities (indicated STA A, STA B inthe figure) located within a coverage area Cl (also denoted cell) beingserved by the AP. When, for instance, the access point (AP) hassomething to transmit, it performs the CCA procedure. All othertransmitting entities STA A, STA B within its service area Cl will then,at least in a simplified propagation environment, cause the AP to deferits transmissions. It awaits a random back-off time period and thenperforms the CCA again.

In current systems a common CCAT is defined for each AP to be used whenperforming channel sensing for transmission to any of the entities STAA, STA B, associated to the AP. The entities STA A, STA B also use thiscommon CCAT as criterion for deciding whether or not to transmit aframe.

With such static CCAT, a STA (APs and other entities) may refrain fromaccessing the wireless medium since it is also exposed to transmissionsin neighboring AP areas, although simultaneous transmissions would bepossible without increased risk of lost packets and subsequentretransmissions. This limits the performance of the current systems,especially as the CCAT used today is set rather conservatively to −82dBm.

The use of dynamic thresholds has therefore been discussed. If the STAscould adapt their carrier sensing threshold dynamically then the amountof simultaneous transmissions in the system might be increased withoutsignificantly increasing the probability of collisions within andbetween the different areas.

Referring again to FIG. 1, when an entity has a frame to transmit (box1), it again assesses if a channel is busy by scanning (box 2) thechannel. However, in the case of a dynamic CCAT, instead of the fixedCCAT (exemplified by −82 dBm in the figure) the entity uses thedynamically set CCAT for establishing whether the received signalstrength level is such that the entity should defer its transmission orperform the transmission. Various suggestions have been presented on howto set the dynamic thresholds. Some studies have shown that adjustingthe CCAT to a more aggressive value provides throughput increases forboth the mean and 5th percentile user throughputs.

Even though the dynamic adjustment of the CCAT would, in many scenarios,lead to improved system performance in terms of spectrum usage andsystem throughput, there is a tendency of also increasing the number offailed transmissions. The reason for this is that when a certain STA(either AP or non-AP STA) attempts to use the channel by applying a moreaggressive channel access mechanism and then transmit simultaneouslywith an already on-going transmission, it creates additionalinterference which might lead to losses for the on-going transmissionand resulting in re-transmissions.

There is a need for improving system throughput and spectrum usage byenabling simultaneous transmissions while still keeping the number ofre-transmissions to a minimum.

SUMMARY

An objective of the present teachings is to address the above issue andto solve the above mentioned problem.

The objective is according to an aspect achieved by a method performedin an entity for transmitting in a communications system. The methodcomprises assessing a channel to be available for transmission byestablishing an on-going transmission to have a received signal strengthsuch as to allow simultaneous transmission in view of a first clearchannel assessment threshold; establishing type of transmission of theon-going transmission; and determining, based on the established type oftransmission, whether to transmit or to defer transmitting.

The method provides a mechanism for e.g. a WLAN system to excludecertain types of high-impact transmissions from being subject to thetrade-off between, on the one hand, spatially reusing the channel andthereby improving spectral efficiency and user and/or system throughput,and, on the other hand, increasing the number of failed transmissions,which is inherent to the channel access that is based on dynamic CCATcontrol.

In an embodiment, the determining comprises determining to defertransmitting if the type of transmission comprises a first type and elsedetermining to transmit simultaneously. The first type of transmissionmay, for instance, comprise a transmission that is of high importanceand/or high impact in some sense, e.g. a transmission comprising controlinformation or a transmission to multiple users, which, if lost, wouldcause high impact by causing many retransmissions. An entity wanting toperform a transmission and checking if the channel is available willrefrain from transmitting even though it would be allowed to transmitbased on the use of dynamic adjustment of the CCAT. Thereby thesehigh-importance or high-impact transmissions are protected from beingsubjected to increased interference and the accompanying increased riskof being lost.

In some embodiments, the determining is further based on a second clearchannel assessment threshold and the determining comprises determiningto transmit simultaneously if the on-going transmission has a receivedsignal strength such as to allow simultaneous transmission in view ofthe second clear channel assessment threshold. For instance, the firstclear channel assessment threshold may be a threshold of a dynamicallyadjusted CCAT method. If the on-going transmission is established tohave a received signal strength such as to allow simultaneoustransmission in view of the first CCAT (i.e. channel is clear), but thatthe type of transmission is such that the entity would need to defer itstransmission, another check may be performed which is less aggressive inallowing channel reuse. The second check may use a conservativethreshold whereby the transmission of the entity wishing to transmitwould cause limited interference to the on-going transmission. An evenfurther increased channel reuse is obtained while still protecting e.g.high-importance or high-impact transmissions.

The objective is according to an aspect achieved by a computer programfor an entity for handling transmissions. The computer program comprisescomputer program code, which, when executed on at least one processor onthe entity causes the entity to perform the method as above.

The objective is according to an aspect achieved by a computer programproduct comprising a computer program as above and a computer readablemeans on which the computer program is stored.

The objective is according to an aspect achieved by an entity fortransmitting in a communications system. The entity is configured to:assess a channel to be available for transmission by establishing anon-going transmission to have a received signal strength such as toallow simultaneous transmission in view of a first clear channelassessment threshold; establish type of transmission of the on-goingtransmission; and determine, based on the established type oftransmission, whether to transmit or to defer transmitting.

Further features and advantages of the embodiments of the presentteachings will become clear upon reading the following description andthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart illustrating principles of a clear channelassessment in a wireless network.

FIG. 2 illustrates a wireless network in which clear channel assessmentis used.

FIG. 3 illustrates schematically an environment in which embodimentsaccording to the present teachings may be implemented.

FIG. 4 is a flow chart illustrating a first channel assessment principlein accordance with the present teachings.

FIG. 5 is a flow chart illustrating a second channel assessmentprinciple in accordance with the present teachings.

FIG. 6 illustrates a flow chart over steps of an embodiment of a methodin an entity in accordance with the present teachings.

FIG. 7 illustrates schematically an entity and means for implementingembodiments of the method in accordance with the present teachings.

FIG. 8 illustrates an entity comprising function modules/softwaremodules for implementing embodiments in accordance with the presentteachings.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth such as particulararchitectures, interfaces, techniques, etc. in order to provide athorough understanding. In other instances, detailed descriptions ofwell-known devices, circuits, and methods are omitted so as not toobscure the description with unnecessary detail. Same reference numeralsrefer to same or similar elements throughout the description.

The inventors behind the present teachings have pinpointed an existingtrade-off between possible channel reuse, i.e. possibility of performinga transmission simultaneously with on-going transmissions, and thecreation of additional interference to the on-going transmissions, andprovided methods and devices for improving on the situation for bothparts, i.e. for the transmitting part and the part wanting to transmitsimultaneously.

According to the present teachings, certain types of transmissions,referred to as “high-impact transmissions” herein, are given specialconsideration when channel access is performed based on dynamicsensitivity thresholds adjustment. There may be various reasons forgiving special consideration for certain types of transmission (and notto others). A transmission may for instance be categorized as ahigh-impact transmission based on the number of users being addressed bythe particular transmission. The transmission may, for instance, be anorthogonal frequency division multiple access (OFDMA) transmission ormulti-user multiple-input multiple-output (MU-MIMO) transmission. Otherexamples on a high-impact transmission comprise the importance of theinformation being carried in the transmission, e.g. control messagessuch as request to send (RTS) message, clear to send (CTS) message,acknowledgement (ACK) messages, etc.

In various embodiments according to the present teachings, a method forselective dynamic sensitivity threshold adjustment is provided, wherebychannel access based on dynamic sensitivity threshold adjustment isdisallowed if the on-going transmission is considered to be ahigh-impact transmission. Thus, the reliability of high-impacttransmissions is improved and these transmissions are not affected bythe trade-off outlined earlier.

FIG. 3 illustrates schematically an environment in which embodimentsaccording to the present teachings may be implemented. A wirelesscommunications system 10 is illustrated, which may comprise e.g. a Wi-Finetwork, also known as WLAN (the terms are used interchangeably herein).WLAN is standardized in the 802.11 specifications, in particular in IEEEStandard for Information technology—Tele-communications and informationexchange between systems. Local and metropolitan area networks—Specificrequirements. Part 11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) Specifications).

As a note on vocabulary, a station (STA) may be an access point (AP)providing access to user stations or it may be a user station STA, i.e.a non-AP STA. The method described herein is applicable to, and may beimplemented in, all entities (APs and non-APs) that want to transmit ina wireless communications system, e.g. a WLAN.

The wireless communications system 10 may comprise a number of STAs 11,11 a, 11 b, 12, 13, including APs 12, 13 as well as user stations 11, 11a, 11 b (non-AP STAs). Each AP 12, 13 have a number of STAs 11 a, 11 b,11 c associated to it.

The STAs 11, 12 of the wireless communications system 10 are arranged to(e.g. configured to) perform CCA based on dynamic adjustment of the usedCCAT. The CCAT may be dynamically selected in various ways, e.g.depending on load in a STA (in particular load in AP), based onthroughput for STAs, distance between transmitting and receiving STAsetc. The dynamic CCATs could, for instance, be set per frame or per sometime unit.

In an embodiment according to the present teachings, when a STA 11, 12(either an AP STA or a non-AP STA) performs a clear channel assessment,it employs a mechanism for selective dynamic sensitivity thresholdadjustment, by which it applies an additional consideration, inparticular considers the type of the on-going transmission that it hasdetected. If the on-going transmission is determined to be a high-impacttransmission, it does not employ sensing threshold adjustmentmechanisms.

FIG. 4 illustrates a first example of the selective dynamic sensitivitythreshold adjustment algorithm 20 according to the present teachings.

In box 21, a STA 11, 12 has a transmission unit to transmit. In thefollowing the transmission unit is denoted a frame.

In box 22, the STA 11, 12 performs a CCA procedure for the channel(s) inorder to establish whether it may go ahead and transmit the frame. TheCCA procedure has a dynamically adjusted CCAT, as indicated in box 22 by“x dBm”. A first dynamically adjusted CCAT value may for instance be −72dBm (x=−72 dBm). The STA 11, 12 establishes whether any transmission canbe found for which the received signal strength is stronger than thefirst CCAT, i.e. whether the channel is idle or busy. If, in box 22, itis determined that the channel is busy, flow continues to box 23 and theSTA 11, 12 defers its transmission.

If, in box 22, the STA 11, 12 finds the channel to be idle in the sensethat an on-going transmission has a received signal strength that isbelow the first CCAT value, flow continues to box 24. In box 24, eventhough the STA 11, 12 would be allowed to perform its transmissionaccording to the first CCAT value, it checks fulfillment of a secondcriterion before actually performing the transmission. The STA 11, 12checks whether the transmission that it detected is a high-impacttransmission or not. If the detected transmission does not belong tothis type of transmission, then flow continues to box 25 and the STA 11,12 goes ahead with its transmission. If, on the other hand, the detectedtransmission is such a high-impact transmission, then the STA 11, 12refrains from the transmission, and flow continues to box 23. In box 23,the STA 11, 12 defers its transmission, and may e.g. wait a randomback-off period before again checking whether the transmission medium isdeemed idle.

FIG. 5 illustrates another embodiment according to the presentteachings, in particular, another example of the selective dynamicsensitivity threshold adjustment algorithm 30 according to the presentteachings.

In box 31, a STA 11, 12 has a frame to transmit.

In box 32, the STA 11, 12 performs a CCA procedure for the channel(s) inorder to establish whether it may go ahead and transmit the frame. TheCCA procedure used has a CCAT that may be dynamically adjusted, asdescribed earlier. The STA 11, 12 establishes whether any transmissioncan be found for which the received signal strength is stronger than thefirst CCAT, i.e. whether the channel is idle or busy. If, in box 32, itis determined that the channel is busy, flow continues to box 33 and theSTA 11, 12 defers its transmission.

If, in box 32, the STA 11, 12 finds the channel to be idle in the sensethat an on-going transmission has a received signal strength that isbelow the first CCAT value, flow continues to box 34.

In box 34, even though it would be allowed to, according to the firstCCAT value, perform its transmission, the STA 11, 12 checks fulfillmentof a second criterion before actually performing the transmission. TheSTA 11, 12 checks whether the transmission that it detected is ahigh-impact transmission or not, just like in the first algorithmdescribed with reference to FIG. 4. If the detected transmission is sucha high-impact transmission, flow continues to box 36.

In box 36, a third criterion is applied to determine whether or not totransmit the frame. The STA 11, 12 uses a second CCAT value in order todetermine whether or not to transmit its frame. If the received signalstrength of the detected transmission is higher than the second CCATvalue, then flow continues to box 33 and the STA 11, 12 defers itstransmission. The second CCAT value may be a more conservatively setthreshold value, e.g. as the legacy static legacy CCAT, while thedynamically set CCAT value (box 32) may be a more “aggressively” setthreshold value, allowing a higher number of simultaneous transmissions.

However, if the signal strength of the detected transmission is lowerthan the second CCAT then the STA 11, 12 goes ahead with thetransmission of the frame anyway, i.e. simultaneously with the alreadyon-going transmission.

The second CCAT is a less aggressive (more conservative) threshold thanthe first CCAT (box 32), whereby it is ensured that the on-goingtransmission is “heard” by the STA 11, 12 at such low signal strengthlevel that it is not likely that its transmission in turn would causeinterference to the on-going transmission, at least not to such anextent that the on-going transmission would fail. The STA 11, 12performing the check and the station with the on-going transmission mayfor instance be located far apart from each other and it may be assumedthat the transmissions will not interfere with each other to any highextent.

If, in box 34, the detected transmission does not belong to thehigh-impact type of transmission, then flow continues to box 35 and theSTA 11, 12 goes ahead with its transmission.

In this second algorithm, when the STA 11, 12 evaluates the on-goingtransmission (box 32) and determines that it is indeed a high-impact one(box 34), it may revert back to using (box 36) a legacy CCAT with only afixed CCAT (e.g. −82 dBm) in order to protect the high-impacttransmission from additional interference.

In another embodiment, when a STA 11, 12 evaluates the on-goingtransmission and determines that it is indeed a high-impact one, itemploys a less aggressive channel reuse mechanism (i.e. mechanism fordetermining whether a simultaneous transmission would be too interferingor not). Assuming for instance, that the STA 11, 12 is using a dynamicsensitivity threshold algorithm that yields, for instance based on loadof the AP, a CCAT value of −62 dBm to be used when assessing the channelfor a simultaneous transmission. Then, after determining that aparticular on-going transmission is a high-impact one, the STA 11, 12may use a lower value (<−62 dBm) for this particular simultaneoustransmission occurrence.

In various embodiments, only particular types of transmissions aredetermined as being high-impact transmissions. One set of transmissionsthat may be classified as high-impact transmissions could be all multiuser transmissions, i.e., transmissions that involve more than onereceiving or transmitting device. These transmissions may, for instance,comprise all downlink and/or uplink OFDMA transmissions, and/or alldownlink and/or uplink MU-MIMO transmissions. Another set oftransmissions that could be classified as high-impact transmissions aretransmissions related to control signaling, e.g. all IEEE 802.11 Controlframes, comprising for instance request-to-send (RTS), clear-to-send(CTS), acknowledgements (ACKs), Poll frames, Very High Throughput NullData Packet (VHT NDP) frames, etc.

In various embodiments, the STA 11, 12 may in different ways determinewhether a particular transmission is to be considered as high-impacttransmission. The STA 11, 12 may be configured to recognize thehigh-impact transmission types. One way to do this determination is todecode a MAC header of a frame from the on-going transmission andcompare to a number of different types of frames that have beenclassified as high-impact frames. Another way is to decode a framepreceding the high-impact frames (i.e. high impact transmission) andthus acquire a priori information that a high-impact transmission willfollow. For instance, many multi-user transmissions are preceded by aso-called “trigger frame”, and a STA 11, 12 that wishes to perform asimultaneous transmission, could identify an up-coming high-impacttransmission based on their “trigger frame”.

In various embodiments, a physical layer (PHY) header is used in orderto determine whether an overheard transmission (a frame thereof) is of a“high-impact” transmission type. The PHY header may comprise informationrelated to multi-user reception. For instance, one field of a VHT signalA (VHT-SIG-A) is the “Group ID” field. This field has a value of 0 or 63for single user frames, while a value between 1 and 62 indicates thatthe frame is addressed to multiple receivers. Hence, the STA 11, 12 maydeduce that the transmission is intended for multiple receivers and thusestablish that it is a high-impact transmission.

In summary, the present teachings provide a method, and an entityperforming the method, by which the channel access based on selectivelyapplying dynamic sensitivity threshold adjustment is based also on typeof on-going transmission. If the on-going transmission is considered tobe a high-profile one (e.g., OFDMA, MU-MIMO, RTS/CTS/ACK frame, etc.)then dynamic sensitivity threshold adjustment is either not applied orless aggressive threshold values are used.

The various embodiments and features that have been described may becombined in different ways, examples of which are given in the followingwith reference first to FIG. 6.

FIG. 6 illustrates a flow chart over steps of an embodiment of a methodin an entity in accordance with the present teachings.

A method 50 for transmitting in a communications system 10 is providedthat may be performed in an entity 11, 12. The method 50 comprisesassessing 51 a channel to be available for transmission by establishingan on-going transmission to have a received signal strength such as toallow simultaneous transmission in view of a first clear channelassessment threshold.

The method 50 comprises establishing 52 type of transmission of theon-going transmission.

The method 50 comprises determining 53, based on the established type oftransmission, whether to transmit or to defer transmitting.

In an embodiment, the determining 53 comprises determining to defertransmitting if the type of transmission comprises a first type and elsedetermining to transmit simultaneously.

In various embodiments, the determining 53 is further based on a secondclear channel assessment threshold.

In a variation of the above embodiment, the establishing 52 comprisesestablishing that the on-going transmission is of a first type, andwherein the determining 53 comprises determining to transmitsimultaneously if the on-going transmission has a received signalstrength such as to allow simultaneous transmission in view of thesecond clear channel assessment threshold.

In various embodiments, the first type of transmission comprises one ormore of: a transmission addressed to two or more recipients, atransmission carrying information classified as important, atransmission comprising a request-to-send message, a transmissioncomprising a clear-to-send message, a multi-user multiple input multipleoutput, MU-MIMO, transmission, an orthogonal frequency division multipleaccess, OFDMA, transmission, a beacon frame, a control frame, a triggerframe preceding a first type of transmission.

In various embodiments, the establishing 52 type of transmissioncomprises decoding a medium access control, MAC, header and establishingtype of transmission based on information in the MAC header. In otherembodiments, the establishing 52 type of transmission comprises decodinga physical layer, PHY, header and establishing type of transmissionbased on information in the PHY header.

In various embodiments, the establishing 52 type of transmissioncomprises decoding a trigger frame preceding a first type oftransmission and establishing type of transmission based on the triggerframe.

In various embodiments, the assessing 51 comprises establishing thefirst clear channel assessment threshold by a dynamic sensitivitythreshold adjustment method.

FIG. 7 illustrates schematically an entity and means for implementingembodiments of the method in accordance with the present teachings.

The entity 11, 12 comprises a processor 60 comprising any combination ofone or more of a central processing unit (CPU), multiprocessor,microcontroller, digital signal processor (DSP), application specificintegrated circuit etc. capable of executing software instructionsstored in a memory 61 which can thus be a computer program product 61.The processor 60 can be configured to execute any of the variousembodiments of the method for instance as described in relation to FIG.6.

The memory 61 can be any combination of read and write memory (RAM) andread only memory (ROM), Flash memory, magnetic tape, Compact Disc(CD)-ROM, digital versatile disc (DVD), Blu-ray disc etc. The memory 61may also comprise persistent storage, which, for example, can be anysingle one or combination of magnetic memory, optical memory, solidstate memory or even remotely mounted memory.

The entity 11, 12 also comprises an input/output device 63 (indicated byI/O in FIG. 7) for communicating with other entities. Such input/outputdevice 63 of the entity 11, 12 may comprise a wireless communicationinterface (e.g. radio interface) and/or wired communication interface.

The entity 11, 12 may also comprise additional processing circuitry,schematically indicated at reference numeral 64, for implementing thevarious embodiments according to the present teachings.

The present teachings provide computer programs 62 for the entity 11,12. The computer program 62 comprises computer program code, which, whenexecuted on at least one processor 60 of the entity 11, 12 causes theentity 11, 12 to perform the method 50 according to any of the describedembodiments thereof.

The present disclosure also encompasses computer program products 61comprising a computer program 62 for implementing the embodiments of themethod as described, and a computer readable means on which the computerprogram 62 is stored. The computer program product 41 may, as mentionedearlier, be any combination of random access memory (RAM) or read onlymemory (ROM), Flash memory, magnetic tape, Compact Disc (CD)-ROM,digital versatile disc (DVD), Blu-ray disc etc.

An entity 11, 12 for transmitting in a communications system 10 isprovided. The entity 11, 12 is configured to: i) assess a channel to beavailable for transmission by establishing an on-going transmission tohave a received signal strength such as to allow simultaneoustransmission in view of a first clear channel assessment threshold, ii)establish type of transmission of the on-going transmission, and iii)determine, based on the established type of transmission, whether totransmit or to defer transmitting.

The entity 11, 12 may be configured to perform the above steps e.g. bycomprising one or more processors 60 and memory 61, the memory 61containing instructions executable by the processor 60, whereby theentity 11, 12 is operative to perform the steps. In case of severalprocessors 60 (not illustrated) they may be configured to perform allsteps of the method 50 or only part of the steps.

In an embodiment, the entity 11, 12 is configured to determine to defertransmitting if the type of transmission comprises a first type and elseto transmit simultaneously.

In various embodiments, the entity 11, 12 is configured to determinefurther based on a second clear channel assessment threshold.

In various embodiments, the entity 11, 12 is establish by establishingthat the on-going transmission is of a first type, and configured todetermine to transmit simultaneously if the on-going transmission has areceived signal strength such as to allow simultaneous transmission inview of the second clear channel assessment threshold.

In various embodiments, the first type of transmission comprises one ormore of: a transmission addressed to two or more recipients, atransmission carrying information classified as important, atransmission comprising a request-to-send message, a transmissioncomprising a clear-to-send message, a multi-user multiple input multipleoutput, MU-MIMO, transmission, an orthogonal frequency division multipleaccess, OFDMA, transmission, a beacon frame, a control frame, a triggerframe preceding a first type of transmission.

In various embodiments, the entity 11, 12 is configured to establishtype of transmission by decoding a medium access control, MAC, headerand configured to establish type of transmission based on information inthe MAC header. In other embodiments, the entity 11, 12 is configured toestablish type of transmission by decoding a physical layer, PHY, headerand configured to establish type of transmission based on information inthe PHY header.

In various embodiments, the entity 11, 12 is configured to establishtype of transmission by decoding a trigger frame preceding a first typeof transmission and configured to establish type of transmission basedon the trigger frame.

In various embodiments, the entity 11, 12 is configured to assess byestablishing the first clear channel assessment threshold by a dynamicsensitivity threshold adjustment method.

FIG. 8 illustrates an entity comprising function modules/softwaremodules for implementing embodiments in accordance with the presentteachings.

In an aspect, means are provided, e.g. function modules or units, thatcan be implemented using software instructions such as computer programexecuting in a processor and/or using hardware, such as applicationspecific integrated circuits, field programmable gate arrays, discretelogical components etc., or any combination thereof.

An entity is provided for transmitting in a communications system. Theentity comprises a first unit 71 for assessing a channel to be availablefor transmission by establishing an on-going transmission to have areceived signal strength such as to allow simultaneous transmission inview of a first clear channel assessment threshold. Such first unit 71may for instance comprise processing circuitry adapted for assessing achannel to be available for transmission by establishing an on-goingtransmission to have a certain received signal strength (e.g. unit 61,62 and/or 64 described with reference to FIG. 7).

The entity comprises a second unit 72 for establishing type oftransmission of the on-going transmission. Such second unit 72 may forinstance comprise processing circuitry adapted for establishing type oftransmission (e.g. unit 61, 62 and/or 64 described with reference toFIG. 7).

The entity comprises a third unit 73 for determining, based on theestablished type of transmission, whether to transmit or to defertransmitting. Such third unit 73 may for instance comprise processingcircuitry adapted for determining, based on the established type oftransmission, whether to transmit or to defer transmitting (e.g. unit61, 62 and/or 64 described with reference to FIG. 7).

The invention has mainly been described herein with reference to a fewembodiments. However, as is appreciated by a person skilled in the art,other embodiments than the particular ones disclosed herein are equallypossible within the scope of the invention, as defined by the appendedpatent claims.

The invention claimed is:
 1. A method for transmitting frames, themethod comprising: assessing a channel to be available for transmissionby establishing, based on a first clear channel assessment (CCA)threshold, that a received signal strength of an on-going transmissionallows simultaneous transmission; establishing a type of transmission ofthe on-going transmission on the channel; and determining, based on theestablished type of transmission and on a second CCA threshold that isdifferent than the first CCA threshold, whether to transmit or to defertransmitting and to transmit simultaneously if the on-going transmissionhas a received signal strength such as to allow simultaneoustransmission in view of the second clear channel assessment threshold.2. The method of claim 1, wherein the determining comprises determiningto defer transmitting if the type of on-going transmission is a firsttype.
 3. The method of claim 2, wherein the first type of transmissioncomprises one or more of: a transmission addressed to two or morerecipients, a transmission carrying information classified as important,a transmission comprising a request-to-send message, a transmissioncomprising a clear-to-send message, a multi-user multiple input multipleoutput transmission, an orthogonal frequency division multiple accesstransmission, a beacon frame, a control frame, or a trigger framepreceding a first type of transmission.
 4. The method of claim 1,wherein establishing the type of on-going transmission comprises:decoding a medium access control, MAC, header and establishing type oftransmission based on information in the MAC header, or decoding aphysical layer (PHY) header and establishing type of transmission basedon information in the PHY header.
 5. The method of claim 1, whereinestablishing the type of transmission comprises: decoding a triggerframe preceding a first type of transmission and establishing type oftransmission based on the trigger frame.
 6. The method of claim 1,wherein the assessing comprises establishing the first clear channelassessment threshold by a dynamic sensitivity threshold adjustmentmethod.
 7. The method of claim 1, wherein determining the transmissiontype for the on-going transmission comprises determining whether theon-going transmission is an orthogonal frequency division multipleaccess (OFDM) transmission.
 8. The method of claim 1, whereindetermining the transmission type for the on-going transmissioncomprises determining whether the on-going transmission carries acontrol message.
 9. A computer program product comprising anon-transitory computer readable medium storing a computer program forhandling transmissions, the computer program comprising computer programcode, which, when executed on at least one processor of an entity causesthe entity to: assess a channel to be available for transmission byestablishing, based on a first clear channel assessment (CCA) threshold,that a received signal strength of an on-going transmission allowssimultaneous transmission; establish a type of transmission of theon-going transmission on the channel; and determine, based on theestablished type of transmission and on a second CCA threshold that isdifferent than the first CCA threshold, whether to transmit or to defertransmitting and to transmit simultaneously if the on-going transmissionhas a received signal strength such as to allow simultaneoustransmission in view of the second clear channel assessment threshold.10. The computer program product of claim 9, wherein the computerprogram comprises computer program code for configuring the entity suchthat the entity defers transmitting if the type of on-going transmissionis a first type.
 11. An entity for transmitting in a communicationssystem, the entity comprising: a receiver; a transmitter; a memory; anda processor coupled to the memory, wherein the entity is configured to:assess a channel to be available for transmission by establishing, basedon a first clear channel assessment (CCA) threshold, that a receivedsignal strength of an on-going transmission allows simultaneoustransmission; establish a type of transmission of the on-goingtransmission on the channel; and determine, based on the establishedtype of transmission and on a second CCA threshold that is differentthan the first CCA threshold, whether to transmit or to defertransmitting and to transmit simultaneously if the on-going transmissionhas a received signal strength such as to allow simultaneoustransmission in view of the second clear channel assessment threshold.12. The entity of claim 11, wherein the entity is configured such thatthe entity determines to defer transmitting as a result of determiningthat the type of on-going transmission is a first type.
 13. The entityof claim 11, wherein the first type of transmission comprises one ormore of: a transmission addressed to two or more recipients, atransmission carrying information classified as important, atransmission comprising a request-to-send message, a transmissioncomprising a clear-to-send message, a multi-user multiple input multipleoutput transmission, an orthogonal frequency division multiple accesstransmission, a beacon frame, a control frame, or a trigger framepreceding a first type of transmission.
 14. The entity of claim 11,wherein the entity is configured to establish the type of transmissionby: decoding a medium access control, MAC, header and establishing typeof transmission based on information in the MAC header, or decoding aphysical layer (PHY) header and establishing type of transmission basedon information in the PHY header.
 15. The entity of claim 11, whereinthe entity is configured to establish the type of transmission bydecoding a trigger frame preceding a first type of transmission andestablishing type of transmission based on the trigger frame.
 16. Theentity of claim 11, wherein the entity is configured to establish thefirst clear channel assessment threshold by a dynamic sensitivitythreshold adjustment method.
 17. The entity of claim 11, wherein theentity is configured such that the entity determines the transmissiontype for the on-going transmission by determining whether the on-goingtransmission is an orthogonal frequency division multiple access (OFDM)transmission.
 18. The entity of claim 11, wherein the entity isconfigured such that the entity determines the transmission type for theon-going transmission by determining whether the on-going transmissioncarries a control message.
 19. A method for transmitting frames, themethod comprising: storing a frame to be transmitted; detecting atransmission on a channel; determining a transmission type for thedetected transmission; determining a signal strength of the detectedtransmission; and determining whether to transmit the frame withoutdelay, wherein determining whether to transmit the frame without delaycomprises: 1) determining whether the determined transmission type is afirst transmission type; and 2) comparing the determined signal strengthto a clear channel assessment (CCA) threshold.
 20. The method of claim19, wherein if it is determined that i) the transmission detected on thechannel is not a high-profile transmission and ii) the determined signalstrength is less than the CCA threshold, then the method furthercomprises transmitting the frame without delay.